Most people have no trouble answering the question posed by the title of this book: it was their O-level English teacher, intoning the General Prologue in Middle English, using that silly Norwegian, sing-song accent.

Neverthless, Chaucer lives on as a vibrant genius, the true grandfather of English comedy, by turns honest and ironic, cunning and passionate. And this new book by the Python-turned-medievalist provides a flamboyantly argued, beautifully balanced answer to the question.

Not that it is a question that has ever really been asked before. And by "beautifully balanced", I don't mean that Jones and his co-authors set out to show both sides, but rather the opposite: this is an unashamedly partisan, hell-for-leather attempt to balance a million arguments on the non-existent head of an invisible pin. Because most of the evidence marshalled to prove that Chaucer was murdered arises from silence, from the unsaid, from documents unaccountably missing or unnecessarily altered.

But then that's what makes Jones's canter through medieval politics and literature all the more exciting. The authors take each orthodox view of Chaucer or Richard II or heresy and, one by one, turn them on their heads. It's not the first time Jones has done this - he performed the same trick with his 1980 book about the knight. Previously interpreted as one of Chaucer's three wholly virtuous pilgrims, Jones used all of the poet's careful, lurking omissions to demonstrate that the "parfit gentil knyght" was in fact a cold-blooded, unpatriotic mercenary.

But at the heart of this new journey into medieval silence is one simple question: why is so little known about the end of Geoffrey Chaucer's life? He wasn't only the most famous English poet of his day but also a civil servant and diplomat of considerable standing. And yet his "accepted" death date - October 25, 1400 - is merely inferred from a June 1400 reference to the payment of a £5 annuity and the inscription on his "tomb" in Westminster Abbey, though it turns out that the latter is a cenotaph, constructed by a poetry-loving courtier in 1556.

The central plank of Jones's theory is the 1399 coup which put Henry IV on the throne and Thomas Arundel back behind it. In fact, from the moment he enters the narrative, it's clear that Arundel's the one wearing the black cloak and riding the black horse. And not just because he's the Archbishop of Canterbury. Henry is the chancer, quickly sinking into leprotic dotage, but Arundel is the Machiavellian macht-politician, willing to use theological debate to ensure total submission. And it's this latter "debate" which turned The Canterbury Tales into the (then) longest suicide note in history.

Arundel had grown fat, rich and powerful by holding a succession of bishoprics. Needing now to consolidate a usurper king, the last thing he could stomach was people saying the church was full of fat, rich and power-hungry hypocrites. A hundred years later, Luther managed it but in the late 1390s, the Lollards, as they were known (a pun on a Latin word for weeds among wheat), were just too avant-garde for their own good. Arundel used a campaign against them to secure his and Henry's position. Arundel was the kind of guy to reinstitute public burning for all those who denied the miraculous transubstantiation of the Eucharist. For many true believers this is a genuine article of faith but "for the worldly bishops, the real miracle was that it transformed their critics into heretics".

So the last thing Arundel wanted, Jones argues, was more descriptions of rip-off churchmen. And yet here's Chaucer, using his final masterwork to make everyone laugh at the pardoner who sells fake indulgences to poor congregations; at the summoner (a church court policeman, who probably is the pardoner's significant other) demanding bribes from defendants or will-be-defendants-if-they-don't-cough-up; at the monk spending all his time hunting; and at the friar, who should be penniless but is clearly a pampered, harp-strumming social climber. In fact, it's arguable that the entirety of the Tales - with their gentle mockery of the fake piety of pilgrimages - is an assault on the "church commercial" which relied so heavily on income from pilgrims.

Is this why there is no surviving authorial manuscript of The Canterbury Tales , merely a clutch of unordered fragments? Did Arundel attempt to destroy and suppress it? And is it possible that, by late 1400, Chaucer was locked in one of Arundel's dungeons, being asked to debate heresy with extreme prejudice?

It's a persuasive argument. And there's more. Why, shortly after the coup, did Chaucer suddenly up sticks and rent a house conveniently within the sanctuary of Westminster Abbey? Why does no one record his death contemporaneously when so much more is known about the deaths of many lesser poets? Why are there references to the "tragedie" of his death, that he was "slaughtered"? Why did he write such a strange, all-encompassing retraction at the end of The Canterbury Tales ? And why have the portraits of the pilgrims on the most contemporaneous manuscript been strangely over-painted, making them look less like Chaucer's descriptions and more like good churchmen? Were they, as Jones posits, "enough to make Arundel's crozier curl"?

We'll never know for sure. Even Jones, with all his puppy-dog enthusiasm, has to admit that. But even imagining we did know, what exactly does it add to our image of Chaucer? Jones remains ambivalent as to whether the "political" criticism of the church was accident or design on Chaucer's part. Was he simply recycling the latest jokes about priests or was he deliberately waving a red rag at Arundel, a last hurrah for the intellectually liberated world of Richard's court? Did he imagine that, as favoured court poet, he was safe from barbaric reprisal? Or does he now join a long list, stretching from Ovid to Bulgakov, of writers who accidentally angered their totalitarian masters?

But Chaucer was no unworldly artist, driven solely by his muse - he had served as administrator, diplomat and spy, so such naivety seems unlikely. In this light, The Canterbury Tales suddenly takes on an unsettling and tantalising new dimension: not only poetic and comic masterpiece, but political rallying cry as well.

· Jonathan Myerson's animated film of The Canterbury Tales was nominated for an Oscar in 1998.